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J. Cent. South Univ. Technol. (2011) 18: 1738−1743 DOI: 10.1007/s11771−011−0896−y Production of microbial oils co-fermented by Trichoderma.koningii and Trichosporon cutaneum with Daqu distiller’s grains LI Xin-she(李新社), LU Bu-shi(陆步诗), TANG Wei(唐伟) Department of Biology and Chemistry Engineering, Shaoyang University, Shaoyang 422000, China © Central South University Press and Springer-Verlag Berlin Heidelberg 2011 Abstract: Daqu distiller’s grains were co-fermented as raw materials by Trichoderma.koningii and Trichosporon cutaneum to produce microbial oils, which can provide raw materials for bio-diesel development. The single factor tests were used to investigate the effects of ratio of strains, inoculum size, culture temperature and culture time on the production of microbial oils. The best processing conditions were obtained by orthogonal test through measuring the content of microbial oils in product. The result shows that the microbial oils content of the co-fermented product under the ratio of Trichoderma.koningii to Trichosporon cutaneum of 1:1, the inoculum size of strains of 11% at 28 °C for 6 d is 7.15 g/L. It is shown that the production of microbial oils co-fermented by Trichoderma.koningii and Trichosporon cutaneum with Daqu distiller’s grains is possible. The research provides a new idea for the reuse of Daqu distiller’s grains and also provides a new way for the development of microbial oils. Key words: Daqu distiller’s grains; Trichoderma.koningii; Trichosporon cutaneum; co-fermentation; microbial oils 1 Introduction Increasing exhaust of oil resources has led to the promotion of the research to accelerate the step of the development of alternative fuel diesel in the world. Biodiesel is an ideal alternative to petroleum diesel because of its outstanding characteristically environmental protection and renewable characteristics. At present, biodiesel is mainly made from vegetable oil, animal fats and restaurant waste oil etc which account for 70%−85% of the total production costs [1]. Impacted by the source of raw materials and their cost, the industrial production is at low level and the economic feasibility is poor. Looking for a cheap, high-yield, clean and environmentally friendly micro-oil raw materials becomes the key to the industrialization of biodiesel. Microbial oil is also known as single cell oil. It is stored in yeast, mold, algae and other oil-producing microorganisms under certain conditions. There are many advantages to produce microbial oil. The microorganisms breed quickly, which can shorten the production cycle; the raw materials are rich and cheap which can lower the cost; the production is not affected by season and climate and easy to cultivate in large scale [2]. Daqu liquor is unique traditional liquor in China. After fermentation, the waste which is called distiller’s Foundation item: Project(10A110) supported by Hunan Provincial Education Department of China; Project(2010JT4055) supported by Hunan Provincial Science & Technology Department of China Received date: 20−−; Accepted date: 201−− Corresponding author: LU Bu-shi, Professor; Tel: +86−739−5432229; E-mail: xindalut@163.com grain is usually discarded. According to statistics, the annual distiller’s grains in China are more than 25 million tons. Because of its high acidity, high moisture content and difficulty to be processed, Daqu distiller’s grains are usually discarded which can cause large waste and pollution. According to the report, the distiller’s dried grains contain 18%−20% of crude fiber, 8% crude protein, 6%−7% starch, about 1% of crude fat and amino acids, organic acids, a small amount of ethanol, vitamin etc [3], which can provide carbon sources, nitrogen sources and a variety of minerals for microorganisms. The production of microbial oils fermented by microorganisms with Daqu distiller’s grains which can provide raw materials for bio-diesel development is very important. It is not only cheap and can turn waste into treasure, but also easy to culture in large-scale industrialization. Compared with other ways, microbial conversion is considered more environmentally friendly and less energy consumpting. Literatures showed that Daqu distiller’s grains were mainly used to produce refermentative wine [4−5], fermented feed [6−10], soy sauce [11−12], vinegar [13], activated carbon [14], organic fertilizer [15] etc. So far, there are few reports [16] on the production of microbial oils fermented by microorganisms with Daqu distiller’s grains. The objectives of this study are to investigate the process conditions of the production of microbial oils